1. Field of the Invention
The present invention relates to an image forming apparatus using an electrophotographic process, such as a copying machine and a printer.
2. Related Background Art
FIG. 5 is a cross-sectional view of an image forming apparatus. As shown in FIG. 5, in a conventional image forming apparatus 30, a photosensitive drum 38 is provided inside the apparatus. A charger 35 and a developing unit 36 are provided adjacently around the photosensitive drum 38. Moreover, a transfer unit 37 and a fixing device 40 are disposed around the photosensitive drum 38.
Moreover, a light scanning unit 10 is provided in the vicinity of to the photosensitive drum 38. Furthermore, a sheet of paper 42, and feed and transport rollers 43, 44, 45 capable of successively transporting the sheet of paper 42 are provided below the photosensitive drum 38. Moreover, an image information controller 33 and a reader unit 32 capable of reading an original are provided above the photosensitive drum 38 in an upper part of the image forming apparatus 30.
The light scanning unit 10 provided in the image forming apparatus 30 is for writing on the photosensitive drum 38 using a laser beam. FIG. 6 is a schematic diagram of a side inner part of the light scanning unit 10.
As shown in FIG. 6, the light scanning unit 10 has a structure contained in an optical box 20. That is, the light scanning unit 10 comprises a semiconductor laser as the light source, a collimator lens and a cylinder lens (not shown), a polygon mirror 19, scanning lenses 21, 22, turn-back mirrors 25, 26, 27, a lengthy cylinder lens 29, and an irradiation window 28 in the optical box 20.
Moreover, a laser beam through inside the light scanning unit 10 shown in FIG. 6 is first outputted from the semiconductor laser, collimated by the collimator lens so as to be inputted in the polygon mirror 19, and deflected by the polygon mirror 19. Then, the laser beam passes through inside the optical box 20 so as to be reflected successively by the turn-back mirrors 25, 26. Accordingly, the laser beam is reflected so as to pass through the optical parts in the upper and lower two spaces inside the optical box 20.
The light scanning unit 10 with the above-mentioned configuration is mounted on a frame provided in the image forming apparatus 30 with a high accuracy.
The above-mentioned light scanning unit 10 is replaced per unit due to the life of the parts such as exhaustion of the parts in the market. For the unit replacement, the unit can be replaced after detaching the constituent parts such as the reader unit 32 provided in the main body upper part of the image forming apparatus 30, or the unit can be replaced by sliding and moving from the side of the image forming apparatus 30 without detaching the constituent parts such as the reader unit 32 in the main body upper part.
In the case of the unit replacement after detaching the constituent parts such as the reader unit 32 in the main body upper part in the former case, since the upper part of the image forming apparatus 30 can be opened, the light scanning unit 10 can be fastened using a screw or the like from above. Thereby, the light scanning unit 10 can be fixed stably.
In contrast, in the case of the unit replacement without detaching the constituent parts such as the reader unit 32 in the main body upper part in the latter case, as shown in FIG. 6, an auxiliary part 49 is mounted preliminarily on the light scanning unit 10.
Then, the light scanning unit 10 is guided to a predetermined position in the main body using a rail (not shown) provided in the main body. After abutting against the auxiliary part 49 with a main body fitting part 50 by the guiding operation, the auxiliary part 49 is forced against the main body fitting part 50 sideways using a fixing member such as a screw 51. Thereby, the light scanning unit 10 is provided without movement particularly in the horizontal direction.
However, according to the former method of the two kinds of the detaching and replacing methods for the above-mentioned light scanning unit 10, since all the constituent parts such as the reader unit 32 are detached, excessive labor and long time are required, and thereby the unit replacement itself is extremely inefficient.
In contrast, according to the latter method, the light scanning unit 10 is attached/detached while sliding from the side of the main body without detaching the reader unit 32. In the case of this method, since the light scanning unit 10 can move to a considerably deep part of the main body inside and the reader unit 32 is not detached, it is difficult to fix the light scanning unit 10 from above by a screw or the like.
Furthermore, the light scanning unit 10 is disposed only by abutting in the lateral direction so as to be stabilized using the gravitational force of the light scanning unit 10. Therefore, the close contact property of the light scanning unit 10 to the installation part at the time of fixing is low.
Thereby, an adverse effect is provided to the image quality due to generation of backlash derived from the vibration generated from the light scanning unit 10 itself or the image forming apparatus 30 main body and generation of the error of the installation accuracy itself.
Accordingly, an object of the present invention is to provide an image forming apparatus capable of mounting an optical unit from sideways.
Another object of the present invention is to provide an image forming apparatus with a high stability in an optical unit.
A still another object of the present invention is to provide an image forming apparatus comprising:
an image bearing member;
an optical unit for image exposure of the image bearing member, the optical unit being mountable from sideways of the apparatus main body; and
an elastic member for pressuring the optical unit downward.
A further object of the present invention will be apparent by the explanation provided below.